1. Field of the Invention
The present invention relates to a glass member for optical parts, produced by use of a pulsed laser light, in particular an ultrashort pulsed laser light having a time period of no greater than 10−12 second such as a femtosecond (10−15) pulse, and a glass composition used therefor.
2. Description of the Related Art
It is publicly known that ultrashort pulsed lasers in particular those laser lights having a pulse width on femtosecond level can realize a three-dimensional processing within transparent materials such as glass using a multiphoton absorption process on the basis of strong peak power thereof, and a method of constructing a stereoscopic light waveguide is disclosed in which a high refractive index region is formed inside a glass by focused irradiation of a laser light, as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 09-311237.
Furthermore, a light waveguide and a photonic crystal structure having a high refractive index area are proposed in which a fine crystal of a compound semiconductor is deposited to grow by irradiating an ultrashort pulsed laser inside a base glass where the compound semiconductor is dispersed in order to obtain a larger refractive index difference, as disclosed in Japanese Unexamined Patent Application, First Publication No. 2005-321421.
Furthermore, an optical part is proposed in which a cavity is formed inside a glass as a portion having a lowered refractive index and the difference between the refractive index of the cavity and the refractive index of non-laser irradiated portions is utilized as disclosed in M. Watanabe, S. Juodkazis, H-B. Sun, S. Matsuo, and H. Misawa, “Transmission and photoluminescence image of three-dimensional memory in vitreous silica”, Applied Physics Lett, Vol. 74, No. 26, (1999) pp 3957-3959. For example, a three-dimensional photonic crystal structure is publicly known in which cavities are laminated like a face-centered cubic lattice structure inside a silica glass doped with 10% Ge.